1. Field of the Invention
The present invention relates to a tool exchange apparatus provided for a machine tool such as a punch press, for instance.
2. Description of the Prior Art
A machine tool is often provided with a tool exchange apparatus for automatically exchanging a number of tools to process a workpiece into various shapes or dimensions. In a punch press, for instance, a plurality of tools each composed of a punch and die set are arranged to punch a sheet-like workpiece into products of various shapes and dimensions.
In the case of a turret punch press, a number of punches are mounted on an upper turret and a number of dies are mounted on a lower turret, so that a set of a punch and die can be exchanged by pivoting the upper and lower turrets simultaneously in a relatively short time.
In the case of a punch press provided with a tool magazine and an automatic tool exchange apparatus, however, there exists a problem in that a relatively long time is required to exchange a set of a punch and die.
In more detail, the automatic tool exchange process is as follows: a previous tool (a pair of a punch and die) mounted on the press is removed by the automatic tool exchange apparatus; the removed previous tool is returned to a tool magazine; a new tool arranged on the tool magazine is indexed (while the exchange apparatus stands by); the indexed new tool is removed from the tool magazine and mounted on the press by the exchange apparatus. In other words, in the conventional tool exchange apparatus, since a previous tool is removed from the punch press and returned to the tool magazine and a new tool is removed from the tool magazine and mounted on the punch press by a single robot (arm) independently, when the tool magazine is being indexed, the tool exchange apparatus is at a standstill, thus resulting in a drawback such that the tool exchange time is relatively long.
Further, in the prior-art tool exchange apparatus, since a set of tools (punch and die) is exchanged simultaneously, when a new workpiece with a thickness different from that of a previous workpiece is punched into the same shape, both the same punch and die should be exchanged to change the clearance between the two. In other words, there exists a problem in that a number of tool sets (punch and die) with different clearances must be previously provided to punch workpieces of different thickness into the same shape of the same dimensions, thus resulting in wasteful tool arrangement.